Method for the production of colorstable furnace oil



April 14, 1959 w. F. JOHNSTON, JR 2,882,225

METHOD FOR THE PRODUCTION oTcoLoR-STABLE FURNACE on. Filed April 1o, 1955 i 1N V EN TOR.

Walker E Joli/:sfondi ATTO/iwf;

United States Patent 'i Walker F. Johnston, Jr., Galveston, Tex., assignor, by mesne assignments, to The American Oil Company Application April 10, 1953, Serial No. 348,016

8 Claims. (Cl. 208-266) This invention relates to heating oils, particularly furnace oils derived from a thermal cracking operation. More particularly "the invention relates to a thermally cracked furnace oil which has good storage color stability.

Petroleum distillates boiling in the heavier-than-gasoline range, i.e., between about 350 and 700 F., are widely used as heating oils, particularly in domestic furnaces. These oils are commonly known as furnace oils or heater oils. These oils may be obtained either by distillation from the crude petroleum itself, i.e., virgin distillates, or derived from the product of various refining operations such as thermal cracking of gas oil or catalytic cracking of gas oil. The use of a thermally cracked distillate in furnace oil creates at least one special problem. The oil in a domestic users tank often stands exposed to atmospheric oxygen, in a vented tank, for several months, e.g., during the summer months when the furnace is not operated. Thermally cracked furnace oils have a tendency to go olf color in such storage, i.e., the oil becomes darker in color. Although thev criterion of color stability is affected by competition, in general it is considered that a satisfactorily color-stable oil is one that has a color of 4 ASTM after six months storage in a tank vented to the atmosphere.

An object of this invention is the production of a satisfactorily color-stable furnace oil derived from a thermal cracking operation. Another object is a process for producing a satisfactorily color-stable furnace oil by the acid treating of a thermally cracked heavier-than-gasoline boiling range distillate. A particular object of the invention is the preparation of a satisfactorily color-stable thermally cracked furnace oil by the acid treating of a thermally cracked distillate followed by the subsequent treatment of the treated distillate with an amount of aqueous caustic solution markedly in excess of that required to neutralize the acid-treated oil. A specific object is the elimination of the usual rerunning operation following acid treatment and caustic neutralization of a thermally cracked furnace oil distillate. Other objects will become apparent in the course of the description of the invention.

It has been found that a furnace oil having satisfactory storage color stability can be produced from a thermally cracked furnace oil distillate boiling in the heavierthan-gasoline range by treating said cracked distillate with an effective amount of sulfuric acid, separating acid 2,882,225 Patented Apr. 14, 1959 ice sludge from the treated distillate, contacting the treated distillate with an aqueous caustic solution containing an amount of alkali metal hydroxide considerably in excess of that amount required to just neutralize the residual acidity present in said treated distillate, and separating a satisfactorily color-stable oil from said aqueous caustic solution.

The heavier-than-gasoline boiling range feed (charge stock) to the process of this distillation is derived from the thermal cracking of petroleum hydrocarbons, i.e., the feed is a so-called thermally cracked distillate which boils in the range between about 350 and 700 F. Preferably the final boiling point, ASTM distillation, should be not more than about 625 F.

The sulfuric acid used in the process may be material prepared entirely from sulfur dioxide or it may be prepared from refinery acid wastes. Thus the' fresh sulfuric acid may be, in refinery parlance, either white acid or black acid. Also, the sulfuric acid may be derived from an operation that requires the use of sulfuric acid wherein the used (spent) acid still retains an effective amount of uncombined H2804. The acid from an operation in which the acid acts as a catalyst is the preferred source of spent acid. For example, the H2804 catalyzed alkylation of butylenes or amylenes and isobutane is an excellent source of acid for the process of this invention.

The process of this invention requires a sulfuric acid having a strength between about and 100 weight percent; preferably acid having a composition of between about and 95% is used. The presence of dissolved carbonaceous material in the acid, c g., in black acid and spent alkylation acid, is not harmful as long as the effective acidity of the acid is between about 80 and 100%.

The amount of sulfuric acid needed in the acid-treating step is dependent upon the quality of the feed to the process. In general at least an effective amount of sulfuric acid must be used. Normally the sulfuric acid usage will be between about 2 and 20 lbs/bbl. of feed. Still more commonly the acid usage will be between about 4 and 12 lbs/bbl.

The aqueous caustic solution utilized in the process of this invention consists essentially of water and an alkali metal hydroxide such as sodium hydroxide and potassium hydroxide. The concentration of alkali metal hydroxide solution does not appear to be critical as long as a suicient amount of alkali metal hydroxide is present in the caustic treating step of the process. In general aqueous caustic solutions containing between about 5 and 50 weight percent of alkali metal hydroxide may be used. It is preferred to use a solution containing between about 15 and 25% as these concentrations appear to produce a somewhat better quality product oil.

While the concentration of the aqueous caustic solution does not appear to be critical, the amount of alkali metal hydroxide present in the caustic treating step(s) is critical. The use of just barely enough caustic to neutralize the acidic materialvdissolved and entrained in the acidtreated distillate does not result in the production of a satisfactorily color-stable furnace oil. The use of the usual excessive amounts, i.e., a total amount of caustic 3 between about 200 and 300% based on the theoretical amount necessary, i.e., 2 or 3 times the theoretical amount, do not produce a satisfactorily color-stable furnace oil.

It has been found that the acid-treated distillate must be contacted with an amount of aqueous caustic solution suflicient in amount to have present in the contacting zone(s) at least about 400% of alkali metal hydroxide based `on the theoretical neutralization quantity. Generally the residual acidity of an acid-treated cracked distillate is independent of the amount and concentration of sulfuric acid used in the acid treating. The theoretical amount of alkali metalrk hydroxide required to just neutralize the acid-treated distillate is about 0.2 lb./bbl. of distillate. Thus lin other'l'angua'g'e'theprocess of this invention requires the use 'of `at least about 0.7 lb. of alkali metal hydroxide, inthefuor'mnf an aqueous lsolution, perba'rrel offend-treated distillate or, very closely, per barrel of feed. Aithough "very large amounts of alkali Vmetal hydroxidefrnay-be used,`thereappears Vto be no real advantage in using more than about 3000%, or about 5.5 lbs./bbl. of feed. I tlis preferred toV use between about 1.5 :and 3.5 lbs. of alkali metal hydroxide per barrel of feed. y

The above caustic usages are predicated upon the presence of a treated oil containing a normal amount of dissolved acidic materials and entraned-acid sludge particles. This normal oil may be readily obtained by the use of a suicient settling time or the use of a coalescer or a moderate degree of centrifuging. vShould the treated oil contain an excessive amount of pepper sludge this fact must be taken into account Yin determining the relative amount of excess caustic'to be used in the caustic treating procedure.

The caustic treating procedure of the process of this invention may be carriedout in two steps. Preferably the irst step should be the simple neutralization of the residual acidity of the acid-treated distillate and the second step should utilize the amount of excess caustic needed to produce a furnace oil of satisfactory color stability. For example, when using the preferred amounts of alkali metal hydroxide the rst step should use about 0.2 lb./bbl. and the second step shoulduse between about 1.3 and 3.3 lbs/bbl. Although more than two stages may be used, there appears to be no advantage over using the same amount of caustic in either a single stage or a two-stage procedure.

The two-stage procedure has an 'economic advantage over the single-stage procedure. It has been found that the aqueous caustic vsolution separated` from the oil may be used again and again in contactingfresh 4quantities of neutral oil from the neutralization step. As many as twelve cycles have been carried out while producing furnace oil of satisfactory color stability.

The temperature of contacting in both the acid-treating and caustic-contacting stages has some effect on the quality of the product oil. Temperatures in excess of about 250 F. have a marked adverse effect on product quality. Lower temperatures may be used as long as the distillate is sufficiently uid to permit effective intermingling of the acid and aqueous caustic and the dis tillate. Broadly the temperature of operation should be between about 30 and 250 F. However, it is preferred 4to operate for reasons of product quality between about '100 and 175 F.

The process involves the contacting of two liquids;

therefore, sufficient pressure must be maintained on the system to keep the materials in the liquidl state.

The utility of the process of'this invention is demonstrated by several examples which show the ete'ct of te`m- The illustrative runs were carried out using two dijercipitation system.

4 f ent feeds. These feeds were obtained by distillation of the liquid product derived from the thermal cracking of gas oils, mainly virgin gas oils. Some of the inspections of these feeds are set out in Table I below.

As has been set out earlier, a thermally cracked furnace oil is considered to be of satisfactory color stability if the oil has a 4 ASTM color after six months storage in a vented tank. Obviously experimental investigations cannot be carried out which involve a six months delay between the test and the nal answer. This laboratory has developed an accelerated test for the determination of color stability. It has been found that the color of a thermally cracked furnace oil, which has been maintained in a 4-oz. sample bottle which is vented to the atmosphere at a temperature of 210 F. for 84 hours, very closely approximates the color of the same furnace oil which has been stored in ar vented tank for six months at moderate atmospheric temperatures. A Herein this accelerated 'test color is -designated Colorf84 hr., ASTM." Itis considered that an oil having a color, 84 hr., ASTM, of 4+ is of satisfactory color stability.

TABLE I Thermal cracking unit furnace oil distillate For purposes of comparison furnace oils were prepared by treating the feeds by two conventional methods. in one conventional method the feed was placed in a l5- gallon cone-bottomed vessel'provided with a bottom draw olf valve and inlets for `introducing air or nitrogen near the bottom of the vessel. The desired amount of sulfuric acid was added to the distillateg'tbe contents of the vessel were agitated with nitrogen for l hour. Nitrogen was used in 'run 8, Table 1I, in order to more closely simulate contacting in a continuous system wherein atmospheric oxgen would be excluded. The contents of the vessel were permitted to settle for `l hour -and then the acid sludge was withdrawn. An amount of Isodium hydroxide in water solution was added to neutralize the residual acidity of the acid-treated distillate. The conventional procedure runs always used about the `amount of caustic typically used in commercial operation, i.e., about 200% based on theoretical requirements. The contents of the vessel were agitated with nitrogen for 30 minutes and were allowed to settle for 30 minutes before the aqueous caustic solution was withdrawn. The neutral oil was passed through a rock salt bed in order to remove haze. The dehazed oil was inspected and the color, 84 hr., ASTM, was determined.

What is considered to be a more ecient method was utilized for runs 1-7, Table II. This procedure vinvolved a flow system wherein the distillate and acid were constantly contacted by means of a centrifugal pump; the acid sludge was removed by an electrical precipitation system; the acid-oil and the aqueous caustic were continuously contacted in a centrifugal pump before being passed to an agitated soaking vessel wherein the desired contacting time was attained; and the aqueous caustic was separated from the neutral oil by means of an electrical pretotal of S runs were carried out on feeds A and B by the above methods. The conditions of treatment and the inspections of the product oil are presented in Table II. In these particular runs the acid used was spent acid derived from the sulfuric acid catalyzed alkylation of butylenes and isobutane. The amount of acid varied from 2.5 to lbs./bbl. of feed. The amount of sodium hydroxide used varied from 130 to 250% of the theoretical requirement. Runs 1 through 7 and 8 show that the color stability of the product oil was unquestionably not satisand 215 F. temperatures when using 2.5 lbs. of 86% spent alkylation acid per barrel of feed. These data clearly indicate that 200% NaOH usage is insufficient to produce a satisfactorily color-stable oil. Further, these data show that within the limit of reproducibility a satisfactorily color-stable oil can be produced when using 500% of NaOH, particularly when operating at the higher temperatures.

In Table IV there are presented the results of using factory. 10 2.5 bbis. of 95% fresh acid per barrel of feed. These TABLE II Run No-. 1 2 3 4 5 7 7 b 8 Feed A A A A A A B A Acid Treating:

Concentration, Wt. Percent 86 86 90 90 90 90 90 86 pe Lbs/Bbl. Feed 2. 5 2. 5 2. 5 5.0 5. 0 10. 0 5. 0 5. 0 Temperature, 110 110 110 110 85 110 115 110 lll'llL/ll/Iinute 400 400 200 200 200 200 400 Caustic Treating:

Concentration, Wt. Percent 5 5 5 5 5 5 5 5 Lbs. NaOH/Bbl. Feed .23 .35 .44` 44 44 .44 .26 Percent of Theoretical 130 200 250 250 250 250 150 210 Temperature, F 110 150 150 150 150 150 115 110 Product Oil: 1

ASTM Dist., F.-

90% Rec'd 530 525 516 521 518 525 616 FBP 614 613 608 621 594 634 726 598 Color, Initial, ASIM 2- 2 2 2 2 1% 3% 2 4 Color, 84 hr., ASTM 5% 5+ 5% 5% 5 5 7 3% 6 Spent acid from the alkylation of butylenes and isobutane (effective acidity) a The color of the 97% overhead obtained by rerurming the product o runs about 3-4.

land 8 would be between b An aliquot of the product oil of run 7 was rerun in an Oldershaw column to 97% overhead-results are for the overhead.

In the commercial production of acid-treated thermally cracked furnace oil, it is customary to rerun the neutral oil. This rerunning operation involves distilling the oil to about 3% bottoms, i.e., a 97% yield of product oil. This rerun oil generally has a satisfactory storage color stability. Run 7b illustrates this operation.

The eiect of temperature, acid usage, and caustic usage on color stability 'of a thermally cracked furnace oil were studied in the following manner: A l-gallon Pyrex bottle was -used as the contacting vessel. To this bottle 2 liters of distillate were added and the distillate was then heated to the desired temperature. The desired quantity of acid was added to the hot distillate and the bottle was shaken by a shaking machine for l0 minutes. The acid sludge was removed from the treated distillate by means of a centrifuge; the centrifuging time was about l0 minutes. The treated distillate was divided into 100 ml. portions. The desired quantity of caustic solution was added to each 100 m1. portion of treated distillate and the two were shaken vigorously at the desired temperature for about 10 minutes. The aqueous caustic solution was removed by centrifuging for about 10` minutes. The product oil was dehazed by passage through a rock salt bed.

Tests were carried out on feed A at various acid usages. Two aqueous caustic solutions were used, namely, 5 weight percent and 20 weight percent of aqueous NaOH. Two types of acid were used, namely, (l) 86% spent alkylation acid and (2) 95% fresh white acid. The results of these runs are presented in Tables III through VI.

In the tables the sodium hydroxide usage is given in terms of percent of the theoretical amount necessary to neutralize the acid oil. These quantities are converted to pounds of NaOH per barrel of feed as a footnote in each table. For simplicity of presentation, Tables III through VI are limited to showing the relationship of treating temperature, caustic usage and product oil color, 84hr., ASTM.

Table III shows the results of operations at 110, 150

data indicate that there is some slight advantage in terms of color stability for the use of fresh acid.

Table V presents data on the use of 5` lbs. of 86% spent alkylation acid per barrel of feed. These data indicate that a somewhat better quality oil is produced at moderate NaOH usages than is obtained when using 2.5 lbs. of acid per barrel.

Table VI presents data when using 10 lbs. of 86% spent alkylation acid per barrel of feed. These data show that a better quality'oil is produced at higher NaOH usages, although at the high temperature some adverse effects appear at the low caustic usage.

TABLE III Effect of treating temperature and caustic usage on product oil color, 84 hr., ASTM.

Feed: A

Acid: 86% spent alkylation Acid usage: 2.5 lbsJbbl. of feed Caustic solutions: 5% and 20% aqueous NaOH n TABLE 1V Ee'ct of irealing temperature and caustic usage ou product oil-color, 84 hr., ASTM.

Feeo, Acid.: 49,5%IB`1SO4 (fresli) Acid usage: 2.5`lb`s.lbbl.\ feed Caustic solutions: and 20% aqueous NaOHy TABLE V Eect of treating temperature and caustic usage on product oil color, 84 hr., ASTM Feed: A Acid: 86% spent alkylation Acid usage: 5.0 lbs/bbl. feed Caustic solutions: 5% and 20% aqueous N aOH Tl'atllig Temp., aF.. 110 150 Color 4. Run Color Run N aO usage, percent of theoreticah* l 200 6 38 5y 43 5 ai at "at 4 s 3% 44 3% 41 3 16 4 42 s 5% aqueous NaO. b 20% aqueous NaOH.

Lbs. NaOH/Bbl. Feed Percent oi Theoretical TABLE v1 Eect of treating temperature and caustic usage on product oil color, 84 hr'., ASTM Feed: A A Acid: 86% spent alkylatiou Acid usage: 10.0 lbs/bbl, feed Caustic solutions: 5% and 20% aqueous N BOE Treating Temp., F 110 150 215 Color Run Color I Run Color Run N eCH Usage, Percent of Theoreticalf* yEl 47 5 52 3 48 5' n, S 58 256+ 49 ,2% 53 2%4- 57 256+ 50 2%4- 54, 2% 59 3 51 3 55 @zur aqueous Neon. '120% aqueous N 20H.

*Percent of Theoretical Lbs. NaOH/Bbl.

Feed

The above data indicate that over the range of conditions taught earlier, it is possible by the process of this invention to produce a satisfactorily color-stable thermally cracked furnace oil without a rernning operation. Furthermore, the data show that there is no further benelcial result from the use of very large amounts of alkali metal hydroxide, even though the use of a 20% aqueous caustic solution produces a somewhat better quality oil than the use' of a 5% solution.

RUN 60 In this run the eiect of a multiple-stage operation in the caustic contacting procedure was used. Using the l5-gallon cone-bottomed vessel, feed A was contacted with 5 lbs. of 86% of spent alkylation acid per barrel of feed. The sludge was withdrawn and the acid oil neutralized, using about 200% of NaOH, based on the theoretical requirement, as a 5% aqueous solution. The aqueous solution was withdrawn. A sample of neutral oil was withdrawn and dehazed by means of a salt lter. The remaining neutral oil was contacted in four separate operations using fresh 20% aqueous NaOH solution in each stage. In each stage the NaOH amounted to 750% based on theoretical, i. e., a total caustic usage of 3200%, based on theoretical. After each stage a sample of oil was withdrawn, dehazed and the color, 84 hr., ASTM, determined. It is pointed out that the sample of oil from stage l'had received a total caustic treat of about l000%, based on theoretical. The color, 84 hr., ASTM, of the oil after each of the four stages of caustic treating, following the neutralization stage, is presented below:

N sOH Usage, Color', 84 Stege Cumulative, Hr., ASTM Percent n This run shows that the use of additional aqueous caustic solution in separate stages over an amount suiliycient to produce a satisfactorily color-stable oil has no beneficial result.

RUN e1.

In this run feed A was treated with acid and neutralization caustic as described in run 60. The neutral oil was divided into twelve portions. One portion was treated with 5% aqueous NaOH solution in an amount equivalent to 3300%, based on theoretical requirement, for neutralizing acid oil. This amounts to 5.8 lbs. of NaOH per barrel of feed. The `aqueous caustic was separated from the product oil and used to treat a second portion of neutral oil. This procedure was repeated until the same aqueous caustic solution had treated all twelve portions of the neutral oil. The color, 84 hr., ASTM, of all the product oils varied between 21/2 and 4; the portions treated at the last of the cycling operation had the darker colors.

The annexed drawing Shows in schematic form an illustrative embodiment of the process of this invention. Many items of process equipment such as pumps have been omitted as' these may be readily added thereto by those skilled in the art.

The feed to this embodiment is a distillate boiling between about 360 and 625 F. which is derived by the thermal cracking of a virgin gas oil. Feed from source 11 is passed through line 12 into mixer 13. Mixer 13 is provided with an internal heat exchanger 14.

Sulfuric acid from source 16 is passed through line 17 into mixer 13. In this embodiment 89% spent alkylation acid is used in an amount of 6 lbs./bbl. of feed.

Mixer 13 may be any type of vessel which provides intimate intermingling of the feed and the acid. Heat exchanger 14 is provided in order to maintain the ternperature of the contacting zone at the desired point. In this illustration the temperature of contacting in mixer 13 is about 160 F.

The mixture of treated distillate and acid are removed from mixer 13 and are passed by way of line 19 into separator 21. Separator 21 may be any form of vessel for separating two immiscible liquids. Acid sludge is withdrawn and sent to disposal by way of line 22.

The treated distillate is withdrawn from separator 21 and is passed by way of line 23 into line 24. An aqueous caustic solution from source 26 is passed by way of line 27 into line 24. Herein the aqueous caustic solution consists of a weight percent NaOH-water solution. A slight excess of NaOH over the theoretical is used to neutralize the acid bodies present in the acid-treated oil. In this illustration about 0.3 1b. of NaOH per barrel of treated distillate is used. The mixed aqueous caustic-treated distillate stream is passed from line 24 into mixer 28. In mixer 28 the two liquids are thoroughly intermingled for a time sufficient to essentially neutralize the treated distillate.

The mixed liquids are passed from mixer 28 by way of line 29 into separator 31. Separator 31 is similar in construction to separator 21. The spent aqueous caustic solution is withdrawn from separator 31 and is passed to waste disposal by way of line 32. The neutral oil is withdrawn from separator 31 and is passed by way of line 33 into line 34.

An aqueous caustic solution from source 36 is passed by way of line 37 into line 34. Herein a 15% NaOH- water` solution is used. Sufficient solution is used to provide 3 lbs. of NaOH per barrel of neutral oil. 'I'he contents of line 34 are passed to mixer 39 where they are thoroughly intermingled for a time about minutes. The time of contacting is not critical. Although the degree of contacting has some important bearing on the length of time required, in general the time of contacting may be between about 5 minutes and 60 minutes.

The mixture of caustic solution and oil are passed by way of line 41 into separator 42. Separator 42 is similar in construction to separator 21. The separated aqueous caustic is withdrawn from separator 42 by Way of line 43. This stream may be recycled to line 37 by way of valved line 44, or it may be passed to waste disposal by way of valved line 46. Normally all of the aqueous caustic solution will be recycled and periodically a portion will be withdrawn to waste with a simultaneous introduction of fresh aqueous caustic from source 36.

The oil is withdrawn from separator 42 and is passed by way of line 48 into the lower portion of coalescer 49. Coalescer 49 is a vertical vessel provided with a bed of material which causes the entrained aqueous caustic particles to coalesce and pass out of the oil. Coalescer 49 may be provided with a bed of rock salt, bre glass, etc. Herein a bed of rock salt is used. Brine is withdrawn from the bottom of coalescer 49 and is passed to waste disposal by way of line 51. The hazefree product oil is withdrawn from the top of coalescer 49 and is passed to storage by way of line S2.

Thus having described the invention, what is claimed 1. A procms for the production of color-stable furnace oil, which process comprises contacting a liquid feed consisting of a thermally cracked petroleum distillate boiling in the heavier-than-gasoline range with sms 75 acid of a concentration between about and 100% in an amount between about 2 and 20 pounds per barrel of said feed, separating acid sludge from liquid treated distillate which contains dissolved and entrained lacidic materials, contacting said treated distillate in the liquid state with aqueous caustic solution containing between about 5 and 50 weight percent of alkali-metal hydroxide, in an amount of lbetween about 850% and 3000% of alkali-metal hydroxide based on the theoretical amount needed to neutralize said distillate, and separating a liquid oil from aqueous caustic solution, said acid contacting step and said aqueous caustic contacting step both being carried out at a temperature between about 30 F. and 250 F., and wherein said liquid oil is characterized by a color of not more than 4+ 84 hour ASTM.

2. The proces of claim l wherein said distillate boilsl between about 350 F. and 700 F.

3. The process of claim 1 wherein said Valkali-metal hydroxide usage is between about 850% and l750%.

4. The process of claim 1 wherein said acid is selected from the class consisting of white acid, black acid and spent alkylation acid.

5. The process of claim 1 wherein said temperature of contacting is between about 100 F. and 175 F.

6. A process of producing a furnace oil which comprises (a) contacting a liquid thermally cracked petroleum distillate boiling in the heavier-than-gasoline range with sulfuric acid at a temperature between about 100 F. and 175 F., said acid having a concentration between about and 95% and being used in an amount between about 4 and 12 pounds per @barrel of said distillate, (b) separating acid sludge from a liquid treated distillate, which distillate contains acidic materials, (c) contacting said treated distillate in the liquid state with an aqueous caustic solution containing between about l5 and 25 weight percent of alkali-metal hydroxide, said solution containing only about that amount of alkali-metal hydroxide needed to neutralize said treated distillate, (d) separating a liquid neutralized distillate from aqueous caustic solution, (e) contacting said neutralized distillate in the liquid state with aqueous caustic solution containing between about 15 and 25 weight percent of alkalimetal hydroxide, in an amount such that the sum of the alkali-metal hydroxide used in the neutralization step (c) and in step (e) is equal to between about 850% and 3000% of the amount of alkali-metal hydroxide theoretically needed to neutralize said treated distillate, the temperature in step (e) Ibeing between about F. and F. and (f) separating aqueous caustic solution from a liquid oil, which liquid oil is characterized by a color of not more than 4+ 84 hour ASTM.

7. The process of claim 6 wherein the alkali-metal hydroxide usage is between about 850% and l750%.

8. The process of claim 6 wherein the aqueous caustic solution separated in step (f) is recycled to step (e).

References Cited in the tile of this patent UNITED STATES PATENTS 968,692 Robinson Aug. 30, 1910 1,784,262 Wheeler et al. Dec. 9, 1930 1,908,924 Schaeffer et al May 16, 1933 2,034,712 Dolbear Mar. 24, 1936 2,157,315 Archibald May 9, 1939 2,252,082 Lloyd et al Aug. l2, 1941 2,267,458 Goldsby Dec. 13, 1941 2,293,208 Lazar et al Aug. 18, 1942 2,388,087 Ryan et al. Oct. 30, 1945 2,721,833 Defoe et al Oct. 25, 1955 2,729,594 Alderson et al Jan. 3, 1956 FOREIGN PATENTS 371,752 Great Britain Apr. 28, 1932 458,113

Canada July 12, 1949 

1. A PROCESS FOR THE PRODUCTION OF COLOR-STABLE FURNACE OIL, WHICH PROCESS COMPRISES CONTACTING A LIQUID FEED CONSISTING OF A THERMALLY CRACKED PETROLEUM DISTILLATE BOILING IN THE HEAVIER-THAN-GASOLINE RANGE WITH SULFURIC ACID OF A CONCENTRATION BETWEEN ABOUT 80% AND 100% IN AN AMOUNT BETWEEN ABOUT 2 AND 20 POUNDS PER BARREL OF SAID FEED, SEPARATING ACID SLUDGE FROM LIQUID TREATED DISTILLATE WHICH CONTAINS DISSOLVED AND ENTRAINED ACIDIC MATERIALS, CONTACTING SAID TREATED DISTILLATE IN THE LIQUID STATE WITH AQUEOUS CAUSTIC SOLUTION CONTAINING BETWEEN ABOUT 5 AND 50 WEIGHT PERCENT OF ALKALI-METAL HYDROXIDE, IN AN AMOUNT OF BETWEEN ABOUT 850% AND 3000% OF ALKALI-METAL HYDROXIDE BASED ON THE THEORETICAL AMOUNT NEEDED TO NEUTRALIZE SAID DISTILLATE, AND SEPARATING A LIQUID OIL FROM AQUEOUS CAUSTIC SOLUTION, SAID ACID CONTACTING STEP AND SAID AQUEOUS CAUSTIC CONTACTING STEP BOTH BEING CARRIED OUT AT A TEMPERATURE BETWEEN ABOUT 30* F. AND 250* F., AND WHEREIN SAID LIQUID OIL IS CHARACTERIZED BY A COLOR OF NOT MORE THAN 4+84 HOUR ASTM. 